Consider the following an argument in favor of Maria Sharapova as the most marketable female tennis player in the world.

The No. 4-ranked Sharapova posted a photo of herself on Instagram in front of the King Arthur coffee shop in the Brisbane Central Business District in Queensland, Australia.

The photo received some 67,800 likes, according to her account.

Gold Coast digital marketing expert Sonja Ceri of Media Junkies told Australia's Courier Mail that the photo was worth nearly $10,000 to the coffee shop and to Brisbane in general.

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Sharapova is the second most popular female athlete on social media, behind only Ronda Rousey, according to The Daily Mail. She has 1.1 million followers on Instagram.

The Russian star's marketability was drawn into a discussion about a possible bias against No. 1 player Serena Williams, as Williams owns an 18-2 record against Sharapova, including a current 17-match winning streak.

Serena won three Grand Slam titles in 2015 and has 21 for her career, one shy of Steffi Graf for second place all-time in the WTA and third all-time behind Graf and Margaret Court, who has 24. But Forbes reported that Sharapova earned $23 million in endorsements in 2015, compared to Williams' $13 million.

"From a money standpoint, she's worth at least three times more from an advertising standpoint [than] what she's getting," Martin Morse, CEO of the MM Group, said of Williams to blackenterprise.com. "If she doesn't demand that and make a stink about it, the executives at Nike certainly aren't going to. It's easy money for them.

"If I were the most dominant player in the world, I would be mad. It's that mentality. She could simply say, 'this is what I'm worth. I'm not going to sign with Nike again unless I'm getting what I'm worth. I dominate this sport.' She's got that kind of leverage."

For now, the two will have to share the No. 1 spotlight -- one in the tennis world and one in the financial world.

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